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Show 184 OLDER PLIOCENE PERIOD. [Ch. XIV. north to south, and about six from east to west. Th~ vents of erupti·o n range enti·r e1 y wl· t 11 ·m a nar row band runmncor north and south, and the branches which we have represented as exten dm. g cas t w ard in the map are formed simply of two lava-streams, those of Castell Follit and Cellent. No. 43. Yolcanic districl of Catalonia. Dr. Maclure, the American geologist, was the first who made known the existence of these volcanos*; and, according to his description, the volcanic i'egion extended over twenty square leagues, from A mer to Massanct. I searched in vain in the en· virons of Massanet, in the Pyrenees, for traces of a lava-current; and I can say with confidence that the adjoined map gives a correct view of the true area of the volcanic action. * Maclurc, Jomn. de Phys., vol. lxvi. p. 219, 1808; cited by"Dnubcny, De· scril>lioll of Volcanos, p. 24. Ch. XIV.J VOLCANOS OF CATALONIA. 185 Geological st-ructure of the district.-The eruptions have burst entirely through secondary rocks, composed in great part of grey and greenish sandstone and conglomerate, with some thick beds of nummulitic limestone. The conglomerate contains pebbles of quartz, limestone, and Lydian stone. The limestone is not only replete with nummulites, but occasionally includes oysters, pectens, and other shells. This system of rocks is very extensively spread throughout Catalonia, one of its members being a red sandstone, to which the celebrated salt-rock of Cardona is subordinate. It is conjectured that the whole belongs to the age of our green-sand and chalk. Near Amer, in the Valley of the Ter, on the southern borders of the region delineated in the map, primary rocks are seen consisting of gneiss, mica-schist, and clay-slate. They run in a line nearly parallel to the Pyrenees, and throw off the secondary strata from their flanks, causing them to dip to the north and north-west. This dip, which is towards the Pyrenees, is connected with a distinct axis of elevation, and prevails through the whole area described in the map, the inclination of the beds being sometimes at an angle of between 40 and 50 degrees. It is evident that the physical geography of the country has undergone no material change since the commencement of the era of the volc~nic eruptions, except such as has resulted from the introduction of new hills of scorire and currents of lava upon the surface. If the lavas could be remelted and poured out again from their respective craters, they would descend the same valleys in which they are now seen, and reoccupy the spaces which they at present fill. The only difference in the external configuration of the fresh lavas would consist in this, that they would nowhere be intersected by ravines, or exhibit marks of erosion by running water. Volcanic cones and lavas.-There are about fourteen distinct cones with craters in this part of Spain, besides several points whence lavas may have issued ; all of them arranged along a narrow line running north and south, as will be seen in the |